Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

LACP and Unidirectional Link Detection


Does LACP support unidirectional link detection like PaGP does in desirable mode?


Re: LACP and Unidirectional Link Detection

Are you sure PAGP supports UDLD. The documentation I see on CCO contradicts that.

See below:

Unidirectional EtherChannels cannot support PAgP or LACP. To create a unidirectional EtherChannel, you must configure the EtherChannel "on" mode.

Ref Link:

Hope it helps.


New Member

Re: LACP and Unidirectional Link Detection

I guess I worded my question incorrectly.

A PaGP etherchannel in desirable mode provides UDLD type functionality. Does LACP provide the same functionality? My guess is yes it does because LACP supports the automatic creation of etherchannels in an active/active or active/passive configuration.

I just can't find documentation to support this.

Re: LACP and Unidirectional Link Detection

Got it.

Yes, the functionality of LACP is very similar to PAGP excepting that LACP is an IEEE standard.

The following link from IEEE explains the inner-working of the protocol.

Here's Cisco's explanation of LACP:

Link Aggregation Control Protocol (LACP) is part of an IEEE specification (802.3ad) that allows you to bundle several physical ports together to form a single logical channel. LACP allows a switch to negotiate an automatic bundle by sending LACP packets to the peer. It performs a similar function as Port Aggregation Protocol (PAgP) with Cisco EtherChannel.



CreatePlease login to create content